fix check idx index

[wgliang]

There happened a panic error in kubernetes seem because it.

kubernetes/kubernetes#64291

[liggitt]

thanks, definitely needs a testcase (or several, exercising the conditions that could panic before)

[alvaroaleman]

Oh, I just happened to write a PR for this as well, didn't notice yours :)

Your checks are more complete thought, maybe you just wanna copy over the test from my PR (#58 ) and I will close it?

[wgliang]

Ok, thank you. I will copy it.

[wgliang]

@evanphx
Please merge it as soon as possible, then I will update the package in kubernetes.
Thanks very much.

[evanphx]

Thanks so much both of you!

[hashier]

NVD https://nvd.nist.gov/vuln/detail/CVE-2018-14632 links here for a CVE. Is this a bug on NVD or is CVE-2018-14632 related to this commit?

Edit:
I guess yes: https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-14632

[alvaroaleman]

@hashier this fixed a bug that resulted in a panic for faulty json patches that specified an out of bounds index. Both Kubernetes and Openshift use this lib which meant it was possible to cause a DOS through an invalid patch (still requires access to the cluster in order to even be able to submit patches). Kube updated this dependency in May 2018 through kubernetes/kubernetes#64355 and I presume Openshift did it around the same timeframe.